Implement Pratt parser.

1 files changed, 88 insertions, 0 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/parserutils/pratt/TokenStream.java b/BJC-Utils2/src/main/java/bjc/utils/parserutils/pratt/TokenStream.java
new file mode 100644
index 0000000..8decc09
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/parserutils/pratt/TokenStream.java
@@ -0,0 +1,88 @@
+package bjc.utils.parserutils.pratt;
+
+import bjc.utils.funcutils.StringUtils;
+import bjc.utils.parserutils.ParserException;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * A stream of tokens.
+ * 
+ * @author EVE
+ *
+ * @param <K>
+ *                The key type of the token.
+ * 
+ * @param <V>
+ *                The value type of the token.
+ */
+public interface TokenStream<K, V> {
+	/**
+	 * The exception thrown when an expectation fails.
+	 * 
+	 * @author EVE
+	 *
+	 */
+	public static class ExpectationException extends ParserException {
+		/**
+		 * Create a new exception with the specified message.
+		 * 
+		 * @param msg
+		 *                The message of the exception.
+		 */
+		public ExpectationException(String msg) {
+			super(msg);
+		}
+	}
+
+	/**
+	 * Get the current token.
+	 * 
+	 * @return The current token.
+	 */
+	Token<K, V> current();
+
+	/**
+	 * Advance to the next token in the stream.
+	 * 
+	 * Has no effect when the end of the stream is reached.
+	 */
+	void next();
+
+	/**
+	 * Utility method for checking that the next token is one of a specific
+	 * set of types, and then consuming it.
+	 * 
+	 * @param expectedKeys
+	 *                The expected values
+	 * 
+	 * @throws ExpectationException
+	 *                 If the token is not one of the expected types.
+	 */
+	default void expect(Set<K> expectedKeys) throws ExpectationException {
+		K curKey = current().getKey();
+
+		if(!expectedKeys.contains(curKey)) {
+			String expectedList = StringUtils.toEnglishList(expectedKeys.toArray(), false);
+
+			throw new ExpectationException("One of '" + expectedList + "' was expected, not " + curKey);
+		} else {
+			next();
+		}
+	}
+
+	/**
+	 * Utility method for checking that the next token is one of a specific
+	 * set of types, and then consuming it.
+	 * 
+	 * @param expectedKeys
+	 *                The expected values
+	 * 
+	 * @throws ExpectationException
+	 *                 If the token is not one of the expected types.
+	 */
+	default void expect(@SuppressWarnings("unchecked") K... expectedKeys) throws ExpectationException {
+		expect(new HashSet<>(Arrays.asList(expectedKeys)));
+	}
+}